Setting up a greenhouse

Greenhouse is a structure with walls and roof made chiefly of transparent material, such as glass, in which plants requiring regulated climatic conditions such as temperature, humidity, air and light are grown.

Greenhouses are classified according to shape:
-Gothic
-A-frame
-Quonset
-Post and Rafter greenhouse

Various materials used for greenhouse framework:
-Steel
-plastic
-Aluminum
-Wood

Various materials used for greenhouse cover include:
-Glass
-Fibre glass
-Rigid double wall plastics
-Plastic films(clear or translucent)
-Polythene sheets

Site selection for greenhouse farming:

-Flat to Gently sloping.
-Adequate lighting from the sun.
-Accessible and reliable water source.
-Well drained site.
-Stable and workable soils/use tubes where the situation is not practical.
-Safe from lines of strong winds.
-Access to source of heat in the temperate zones.
-Proximity to storage/processing area.

Examples of greenhouse suppliers and installers in Kenya include:

-Amiran Kenya Ltd.
-Agro-irrigation Ltd.
-African hydroponics.
-Belbar Engineers.
-Agro-Tunnel international.
-Hort Pro/Irrico Ltd.

Design considerations of a greenhouse:

-Unless you are restricting yourself to growing greenhouse crops such as tomatoes and cucumbers, you will need a bench down at least one side of the greenhouse.

-A shelf above the bench is a useful spot for seedlings.

-If you want to sow from seed and overwinter tender plants in the greenhouse you will need a power source for a propagator and possibly a heated bench and fan heater.

-If you are going to grow greenhouse crops you will need at least one bed, or a space for growbags; growbags can be stood on a bed to maintain a flexible space.

-Ventilation is essential both in the roof (autovents are simplest) and in the sides; latched windows or louvres allow cross ventilation which helps keep the greenhouse cool in hot weather.

-A maximum/minimum thermometer will help you keep an eye on the temperature.

-Internal or external blinds allow flexible shading.

-A paved pathway down the centre of the greenhouse provides easy access; watering it in hot weather causes evaporation which rapidly cools the greenhouse air.

-If you choose a greenhouse with gutters you can harvest the rainwater to use in the greenhouse; it also helps to have a tap in the greenhouse or nearby as a back up.

-A gravel soakaway around the base of the greenhouse will drain excess water away from the building.

-A paved area around the greenhouse will make it easy to maintain.

When operated correctly a greenhouse can give fresh produce throughout the year regardless of the season. The capacity to carefully control the temperature and humidity are important advantages of this farming system.

Greenhouse system enables the use of modern technology such as hydroponics which involves growing plants in soil-less media, in a liquid which can be water infused with specialized nutrient mixes.This allows plants to grow larger and faster than normal, helping to maximize efficiency.

The main disadvantage of greenhouse farming is high cost of buildings construction and maintenance,which in Africa and developing countries can be addressed by organizing smallholders into green house farming groups, in order to pool resources.

While this technology offers numerous advantages, proper techniques are necessary to avoid  the  pitfalls of the technology. If you manage your project well all the year round, you'll need to prepare for the hazards of each season.

In hot season cross-ventilation system is required. Passive ventilation with exhaust openings cut both high and low on the walls may provide sufficient air circulation for small structures. However, some greenhouses require a system of fans to keep the air circulating during the hot season due to high temperatures.In cool weather the circulation will be unnecessary in most cases.

-Soil fertility management practices are vital and they include crop rotation, regular application of compost, mulching, leaving the soil fallow to improve and maintain fertility.

Apply fertilizers according to the soil requirements and the crops to be grown following soil analysis report.

Fumigation or entire change of soil may be required before planting to clear crop pests and diseases. Fumigation involves saturating the greenhouse soil with pesticides like Dioxysan which releases fumes of Chlorine dioxide, (CL2) to control soil pest and diseases

Benefits of greenhouse farming:

-The system increases agricultural output.
-Economizes on space.
-Saves irrigation water.
-Improves farming income.
-Improves food security.
-The technology reduces crop pest and diseases incidences.
-Allows growing of crops not suited to the region due to climate modification.

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